Westcountry farmers say the continued failure of "big players" in the food supply chain to pay a sustainable farm-gate price could lead to ruined businesses and job losses in the wider rural economy.
Large supermarkets are "sucking in cheap imports" rather than helping to underpin the domestic supply base, they claim.
The warning comes after wet weather made 2012 the worst year in living memory for many farmers, combined with an upsurge in the Schmallenberg virus, which threatens to cause higher- than-usual mortality rates during the main lambing season.
Adding to the misery, official figures raise the dire prospect that sheep farmers face losing money with every lamb born, with a price drop of one fifth over the past year – a return to 2009 prices.
Statistics produced by the National Farmers' Union (NFU) show that farmers can expect to lose up to £29 per lamb, prompting the union to appeal to retailers not to play store wars with prices at the expense of producers.
South West NFU livestock board chairman and Dorset farmer Andy Foot has accused the retailers of taking "a short-sighted, short-termist" approach.
He said: "A thriving livestock sector is vital to attracting young people into farming and we are going to need another 60,000 coming into the industry over the next decade to ensure we can continue to fill our own larder.
"Otherwise we will be relying increasingly upon overseas suppliers which won't help our environment, economy and ultimately won't provide the top-quality, good- value food that our farmers are ready, willing and able to deliver."
David Cameron is expected to unveil plans for a groceries industry code of conduct adjudicator in 2013 to stand up for farmers. The watchdog will have the power to "name and shame" big stores who fail to stick to an agreed code of conduct.
The Campaign to Protect Rural England has now joined the growing chorus of support and says the big names need to do more to encourage better management of the region's beautiful landscapes.
It wants the "big seven" to pledge their support for local food producers and pay a "fair price".
The NFU says the region's farmers are still delivering good-quality food, despite everything nature has thrown at them, but that huge volatility, not least in global markets, was being worsened by those further up the food chain, forcing down the price paid to domestic suppliers.
It is calling for retailers to re-think their prices. NFU South West regional director Melanie Squires said: "Farmers are working hard to stay on top of a really tough situation, seeing a considerable reduction in the price that our own retailers pay."
With the EU promising to agree a Common Agricultural Policy reform package in the coming months, the NFU is also stressing the importance of maintaining effective subsidies under the Single Farm Payment scheme.
"If this goes, many sheep farmers and their families face a very uncertain future indeed," she said.
Richard Dodd, spokesman for the British Retail Consortium, said supermarkets were "very supportive" of their own suppliers and could not be held responsible for the fate of an entire agricultural sector. "Supermarkets have to keep the cost down because putting up the shop price wold reduce the amount they sell. They don't buy all the output – there are other customers."
